ELI5- What are blood groups? Why do they differ from person to person? Why can’t a person of one blood group receive blood from a person of a different blood group?

Question

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In: Biology

Answer 1

There are four groups of blood types, A, B, AB, and O. They can all be positive, or negative.

what makes you fall in one of the groups is whether or not you have A and/or B antigens, or none of them:

> A type blood has only A antigens on red blood cells
> B type blood has only B antigens on red blood cells
> AB has both A and B antigens on red blood cells
> O has neither A nor B antigens on red blood cells

As for the plus or minus, that depends on if you have a protein called RhD on your red blood cells (positive meaning you have it, negative meaning you don’t).

The way blood can be transferred works like this: You can only receive blood from blood types that don’t have any antigens you don’t have. So, O can give to any type, A and B can give to AB and their own types, and AB can give to only themselves.

On top of that though, while negative blood types can give to both positive and negative blood, positive blood cannot transfer to negative. So, while O- can give to literally any blood type, O+ can only give to positive ones.